Proteasome Inhibitor Attenuates Skeletal Muscle Reperfusion Injury by Blocking the Pathway of Nuclear Factor-κB Activation

Abstract

Nuclear factor-kappaB is a key transcriptional factor in the regulation of inflammatory factors that are involved in tissue reperfusion injury, but conflicting data have been presented in the literature. The proteasome regulates proteins that control cell-cycle progression and apoptosis, and inhibition of the proteasome has been shown to reduce nuclear factor-kappaB activation and reperfusion injury. Although bortezomib is a potent proteasome inhibitor, its role in skeletal muscle reperfusion injury has not been documented, and its effects on the regulation of inflammatory factors in reperfused tissue are unclear. In this study, the authors investigated the role of nuclear factor-kappaB in skeletal muscle reperfusion injury and the effect of bortezomib (a proteasome inhibitor) on reperfusion injury. Pedicled cremaster muscle flaps from bortezomib-treated and phosphate-buffered saline-treated control mice were subjected to 4.5 hours of ischemia and 90 minutes of reperfusion. During reperfusion, arterial diameters and blood flow recovered earlier and more completely in bortezomib-treated muscle than in controls. Compared with controls, Western blot analysis demonstrated a significant reduction in degradation of nuclear factor-kappaB inhibitory protein and expression of inducible nitric oxide synthase protein in bortezomib-treated muscle at the end of reperfusion. Immunohistochemistry showed decreased nuclear factor-kappaB p65-binding activity and down-regulated protein expression of intercellular adhesion molecule-1 and nitrotyrosine, accompanied by less muscle edema and inflammation as proven by histologic examination. Bortezomib effectively blocks nuclear factor-kappaB activation in attenuating muscle reperfusion injury through inhibiting nuclear factor-kappaB inhibitory protein degradation. Therefore, inhibition of proteasome activity may provide a novel therapeutic strategy for the treatment of skeletal muscle reperfusion injury.